The Ramaroshan Lake Complex (RLC) in Sudurpaschim Province, Nepal, is a Himalayan lake cluster that holds significant ecological, economic, religious, and esthetic importance. This study aimed to provide a comprehensive characterization of the hydrochemical properties of water within the RLC and assess its suitability for irrigation purposes. A total of 38 water samples were collected from seven different lakes of the complex. The physicochemical parameters and major ions were then analyzed. The water samples from the RLC were alkaline, and based on total hardness, they ranged from soft to moderately hard categories. The presence of major ions included the following: Ca²⁺ > Na⁺ > Mg²⁺ > K⁺ > Fe³⁺ > NH₄⁺ and HCO₃⁻ > Cl⁻ > SO₄²⁻ > NO₃⁻ > PO₄³⁻. The alkaline earth metals (Ca²⁺ and Mg²⁺) dominated the alkali metals (Na⁺ and K⁺) and weak acids (HCO₃⁻) dominated the strong acids (Cl⁻ and SO₄²⁻). The dominant hydrochemical facies of the lake water was a Ca-HCO₃ type indicating a calcium carbonate type of lithology. Carbonate rock weathering was the most dominant process in influencing the hydrochemistry of the water. A high ratio of (Ca²⁺+ Mg²⁺)/Tz⁺ and a lower ratio of (Na⁺ + K⁺)/Tz⁺ revealed the dominance of Ca²⁺ and Mg²⁺ resulting from carbonate weathering, with little contribution from silicate weathering. Different irrigation indices revealed the suitability of the RLC water for irrigation. The insights derived from this study are pivotal in safeguarding water quality and bolstering sustainability efforts. The study also furnishes foundational data crucial to an array of stakeholders including researchers and policymakers and significantly contributes to advancing water management strategies and fostering ecosystem conservation in the Himalayan freshwater lakes, particularly in the face of the overarching challenge posed by global climate change.